1. Field of the Invention
The present invention relates to a slider unit that has been extensively used in semiconductor/liquid crystal display manufacturing apparatus, measuring instruments, assembling machines, machine tools, industrial robots, testing instruments, conveyors and others. More particularly it relates to a slider unit having a slider movable lengthwise along an elongated track rail and equipped with a built-in moving-coil linear motor.
2. Description of the Prior Art
The linear motion guide unit is typical of basic and general-purpose devices supporting a striking development in recently advanced mechatronics technology. Although the linear motion guide units have conventionally used incorporated in the apparatus of diverse technical fields, such as machine tools, semiconductor manufacturing machines, material-handling systems, testing instruments, measuring devices, processing machines, assembling machines, industrial robots and others, their use still grow increasingly with the development in technology. In addition, the linear motion guide units recently become required to meet with needs of high precision and high speed in operation, easy assembly, universal application, and so on.
Generally speaking, most linear motion guide units require any sliding means that are installed with the built-in driving means, compact or slim in construction, and able to operate with high propulsion, high speed and high response to provide high speed travel and accurate position control for works, tools, articles and appliances. Linear motors commonly built in the slider units involve two broad types. The first, called moving-magnet linear motor, has a stator of an armature coil arranged lengthwise over the entire length of a bed of stationary part, and a moving-field magnet of permanent magnet arranged on a table movable in a sliding manner along the length of the bed. The second, called moving-coil linear motor, has a stator of field magnet mounted on the bed, and moving-armature coils distributed in space one after another on the table such that they lie a preselected electrical angle out of phase.
A typical example of the prior slider units is composed of an elongated track rail having a U-shape in cross-section, a slider fitting in the U-shaped track rail for freely sliding movement lengthwise the track rail, and driving means to move the slider along the track rail. Japanese Patent Laid-Open No. 307445/1994 discloses a rolling guide unit, which comprises a track rail made in a U-shaped recess in cross-section and arranged in an ellipse, a platform fitting for sliding motion in the U-shaped recess of the track rail, and a motor to drive a pinion meshing with a rack provided on any one of sidewise opposing outside surfaces of the track rail, the motor being arranged on lugs extending sidewise outwardly of the platform. In the construction cited above, the motor projecting above the platform makes it tough to mount a work on the platform.
Another example of the prior slide units is an X-Y stage disclosed in, for instance, Japanese Patent Laid-Open No. 190431/1996. The X-Y stage has a sub-station of U-shape in cross section, a main station movable on the sub-station, and a moving-coil linear motor, or voice-coil linear motor, to drive linearly the main stage. The linear motor in this X-Y stage is also arranged on a base extending sidewise of the main stage, so that the base should requires a broad plane sufficient in area to accommodate both the main stage and linear motor.
A further another example of the conventional slide units is disclosed in, for instance, Japanese Patent Laid-Open No. 38503/1996. The slider unit is composed of a base having a recess of U-shape in cross section, a moving-coil polyphase brushless linear motor built in the base, and a work table movable in a sliding manner along guide rails arranged on sidewise opposing walls of the U-shaped base. In the moving-coil linear motor described just above, permanent magnets are arranged such that the poles on the magnets alternate lengthwise in polarity, and a moving element is arranged for lengthwise movement. The moving element is provided with polyphase coils exposed in a magnetic gap formed on surfaces of the permanent magnets, and field detecting means to control the conducting direction to the polyphase coils. The permanent magnets are arranged spaced apart, while another permanent magnets magnetized lengthwise are alternately arranged and fixed between any adjoining first permanent magnets such that any like polarity comes near on their surfaces, thereby providing a continuous row of permanent magnets. As the moving element in the linear motor travels along the guide rails arranged on the sidewise opposing raised walls of the U-shaped base, the slider unit increases in overall height.
Another example of the conventional slide units is disclosed in, for instance, Japanese Patent Laid-Open No. 140329/1996, which includes a stationary part made in a U-shape in cross section to provide sidewise opposing upright guide rails, a moving part having rollers running along the guide rails, and a moving-magnet linear motor mounted on an upper section of the moving part. According to the prior construction cited above, because of the linear motor arranged above the moving part, it is impossible to attach the works to the moving part. Thus, the construction makes very tough the integration of the works.
Japanese Patent Laid-Open No. 290560/1998 discloses another example of the prior slide units, which includes a pair of linear guides formed in a U-shape in cross section, and a moving-magnet linear motor comprised of stators arranged on the linear guides, each to each guide, and a moving magnet arranged at the center between the stators. As the linear guides are arranged on the stators, a broad plane is required for the stators.
Although the conventional slide units cited above have in general a track rail having an elongated recess of U-shape in cross section, a slider movable in a sliding manner in the recess of U-shape, and driving means to move the slider along the track rail, any of them has the major disadvantages of difficulty in mounting the works and of requiring much area or height for the stationary and moving parts.
Considering that the track rail used in the linear motion guide unit is recessed in cross section to provide high stiffness or rigidity, it will be expected to incorporate the linear motor to drive the slider into the linear motion guide unit, thus not only making the linear motion guide unit compact or slim in construction but also making possible to use the linear motor as the structural member. Moreover, the concept is awaited for making it much easy to mount the work onto the slider, improving in applicability to appliances of diverse fields and in handling of the work.